Seems they are almost ready to release a slip on for both models of the GSX-S. The part number is S-S10SO10-HASZ and no pictures are available. The release date is mid November and price is around $800 US.
The part number is almost identical to the BMW S1000R slip on exhaust. I think the price is pretty steep for a slip on, but my wife does say I'm cheap.
I just want the bike at this point... But if, if I was to upgrade, I think I would go with Yoshi. I have always been fan of Yoahimura's products, but not always their prices. Although I think the Akraprovic does look a little sleeker.
I like the factory exhaust, but getting rid of the cat with a header would always be cool option as well.